Resonance control device



Dc. 16, 1941. LINDNER 2,266,052

RESONANCE CONTROL DEVICE Filed July 30, 1940 2 Sheets-Sheet l I1E=L FIRST FIRST 'vA'RI 'BLE I INPUT HETERODYNE PHASE IIIIIxER OSCILLATOR SHIFT I STAGE 22 STAGE ze sues 24 NETWORK 29' l l saconq SECOND 42 INPUT HETERODYNE 1 MIXER oscI I I,AToR .STAGE 21 STAGE 29 l I F Isa T I SECOND I OUTPUT MIXER smgg as L ATTURIVEY Dec. 16, 1941. H. G. LINDNER 2,266,052

RESONANCE CONTROL DEVICE Filed July 30, 1940 2 Sheets- 'Sheet 2 ILE E FIRST FIRST I] HE TERODYNE INPUT MIXER OSCILLATOR ourpur MIXER I STAGE 22 STAGE 26 STAGE 24- I l j a0 SECOND SECOND NE SECOND VAR/ABLE INPUT MIXER gig i1 3; R OUTPUT MIXER I PHASE SHIFT STAGE 27 STAGE 29 STAGE 28 I NETWORK-29' l I l I 46 EN INVENTOR Herberi G. Lz'ndner Patented Dec. 16, 1941 UNITED STAT 35.:

orrica (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 14 Claims.

This invention relates generally to resonance control devices, and particularly to such devices for maintaining a radio frequency amplifier in resonance with an incoming carrier Wave, especially at the ultra-high frequencies.

An object of this invention is to provide an improved device for resonance control of radio receivers.

Another object of this invention is to provide an improved device to maintain a tuned circuit or circuits of a radio receiver in resonance with thecarrier wave of a transmitter at the ultrahigh frequencies.

A further object of this invention is to utilize the variation of impedance phase angle with frequency, in a sharply-tuned stage of radio frequency amplification in an ultra-high frequency radio receiver, to effect resonance control, so hat the tuned circuit will always be resonant with the incoming ultra-high radio frequency carrier wave.

The development of the ultra-high frequency radio receiver, employing high Q resonant circuits, such as resonant cans, in the radio frequency stages of amplification to obtain very selective circuits, present diflicult problems in the gauging of such circuits. Such highly selective circuits in the receiver also place rather severe limitations on the permissible carrier frequency drift, if the receiver is to remain tuned to the carrier.

My invention overcomes the above. diificulties by automatically keeping the high Q resonant circuit in tune with the incoming ultra-high radio frequency carrier wave once it is tuned to I resonance, and also aids in bringing the circuit in resonance.

My inventionwill be described in connection with the accompanying drawings in which Fig.

1 is a combined block and electrical schematic showing how my device may be used to effect resonance control of a'single stage of radio frequency amplification.

Fig. 2 is an electro-mechanical schematic diagram showing how the motor of U. S. Patent No. 1,959,4i9 is used to rotate the auxiliary tuning capacitor of my invention; and

Fig. 3 is a modification of Fig. 1 and shows how my device can be used to effect resonance of a plurality of ganged radio frequency amplifier stages.

Referring to Fig. 1, the stage H) of radio frequency amplification to which my invention is applied to effect resonance control, includes electron tube II and sharply-tuned circuit l2. Tube i I has at least a grid IS, a cathode l4 and an anode l5, anode I5 being connected to tuned circuit 82, comprising a coil I6, a main tuning capacitor ll and an auxiliary tuning capacitor l8, the movable plates of the latter capacitor being geared or connected to the rotor l8 (Fig. 2) of a tuning motor, described below. The incoming ultra-high frequency carrier is applied to the input 26 of stage I3, and thence to grid l3, the output 2! of stage l0 being applied to the grid of the tube of the following stage. The input of a first input mixer stage 22 is also connected to the input 20 of stage Ii! through resistor 23, the latter being of such magnitude that the mixer tube input impedance does not react on radio frequency stage It. Similarly, the output 2| of stage It is connected to the input of first output mixer stage 24 through resistance 25, this resistance also having such magnitude that the input impedance of mixer stage 2 does not react on radio frequency stage it. The output of frequency controlled ultra-high frequency first heterodyne oscillator stage 26 connects to both mixer stages 22 and 24. The output of first input mixer stage 22 connects to the input of second input mixer stage 21, while the output of first output mixer stage 24 connects to the input of second output mixer stage 28. The output of second heterodyne oscillator stage 29, of fixed frequency, connects to both mixer stages 21 and 28.

The output of mixer stage 28 passes through a variable phase shift network 29', thence through a double-tuned transformer 39, thence through bias source 3|, to the center-tap of the second-'- ary winding of both double-tuned transformers 32 and 33. The output of mixer stage 27 connects to the primary input of both double-tuned transformers 32 and 33. The end terminals of the second Winding of transformer 32 connect respectively to the grids of push-pull demodulator tubes 34 and 35, each such tube having at least a grid, a cathode and an anode. Similarly, the end terminals of the secondary winding of transformer 33 is connected to the grids of push-pull demodulator tubes 36 and 31. The plate load of tubes 34, 35, 36, 3'! consists respectively of the field windings 38, 39, 40 and H of v a synchronous constant reluctance tuning motor such as is described in U. S. Patent No. 1,959,449. Hereinafter the demodulator including tubes 34 and 35 will be referred to as demodulator No. 1, that including tubes 36 and 3'! will be referred to as demodulator No. 2. Capacitors 42, 43, 44 and 45 are radio frequency by-pass capacitors such as are employed in the aforementioned patent.

Each of the aforementioned mixer and heterodyne oscillator stages may include an electron tube with associated circuits as is Well known in the art. First input mixer stage 22 is similar to first output mixer stage 24, while second input mixer stage 21 is similar to second output mixer stage 28. Variable phase shift network 29 may be a lattice type structure similar to the types described in Bell Telephone Laboratories Reprint B342--Distortion correction in electrical circuits, by Otto J. Zobel.

In operation, the incoming carrier is heterodyned with the output of oscillator 26 to produce in mixer 22 a current of the first intermediate frequency. Similarly, the output from stage It] is heterodyned with the output of this same oscillator 26 to produce a current of the first intermediate frequency in mixer stage 24. While the output currents of mixers 22 and 24 are identical in frequency, they may differ in phase, such phase difference being due to the phase shift through ultra-high frequency stage It), mixer stages 22 and 24 being similar. The output of mixers 22 and 24 is fed into mixers 21- and 28, respectively, which such is heterodyned with the output of fixed frequency oscillator 28, to produce a second intermediate frequency, say, of about 460 kcs. Here again, the output current of mixer 21 is identical in frequency with that of mixer stage 28, but these currents will also differ in phase, if there has been any phase shift in stage In.

Variable phaseshift network 29' is initially adjusted to correct for all phase shift between the input current to the primaries of transformers 32 and 33, and the identical-frequency input current to the mid-point of the secondaries of these same transformers, except for the phase shift due to tuned circuit l2.

Transformer 32 is adjusted by detuning the secondary tuning capacitor so that currents passing through it undergo a phase shift of minus 45 degrees. The secondary tuning capacitor of transformer 33 is similarly detuned, but in such a manner that currents passing through it undergo a phase shift of plus 45 degrees, the result being that currents passing through transformer 33 are in phase quadrature with those passing through transformer 32.

When tuned circuit I2 is at resonance with the incoming ultra-high radio frequency carrier from the transmitting station, tuned circuit l2 will cause no phase difference or shift between the input and output currents of stage III, and, as a result of the aforementioned adjustment of network 29', the phase difference between the input current to the primaries of transformers 32and 33, and the input current to the midpoint of the secondaries of these same transformers is also zero. Now as the ultra-high frequency carrier input to stage departs from the resonant frequency of sharply-tuned circuit l2, there will be a phase shift between the primary input current to transformers 32 and 33 and the secondary mid-point input current to these same transformers. This phase shift will vary in magnitude with the magnitude of the frequency departure of the ultrahigh frequency carrier frequency from the resonant frequency of the sharply-tuned circuit l2, and will vary in sign depending upon which side of the resonant frequency of tuned circuit 12 the ultra-high frequency carrier shifts. It will be noted that this phase is not the phase shift through radio frequency stage II), but is the phase shift due alone to tuned circuit l2 of stage [0 being detuned from the incoming carrier frequency. Whatever additional phase shift occurs in stage 10, as for example in tube H, is compensated for by the initial adjustment of network 29'.

The output terminal voltage of transformer 32, as a result of the primary input voltage from mixer 21, may be written as where 51 is the phase shift from the input 20 of stage 10 to the primary input terminals of transformer 32. Similarly, the output terminal voltage of transformer 33, as a result of the primary input voltage from mixer 21, may be written as The terminal output voltage of either transformer 32 or transformer 33, as a result of the secondary midpoint input voltage from transformer 30, and hence from mixer 28, may be written as where (f) is the phase shift due to tuned circuit l2, and 2 is the phase shift from the input 20 of stage ID to the common input mid-point of the secondaries of transformers 32 and 33, exclusive of the phase shift (f). Now (f) is a function of frequency, and tuned circuit l2 being very sharply tuned, this functional relation in the neighborhood of its resonant frequency is very nearly linearly proportional to the frequency departure off resonance.

The resultant output voltage of transformer 32 can then be written as and the resultant output terminal voltage of transformer 33 can be written as E1 Sin [w1t1+45]+E2 sin [w1t2 (f)] For a square law demodulator the plate current is a function of Expanding the square of the last two expres- I sions, we obtain, respectively,

and

Since would contribute only a direct plate current and would produce no motive power in the aforementioned motor of United States Patent No. 1,959,449. However, representing the sharply-tuned resonant circuit phase shift as a function of the frequency departure from resonant frequency, is a variable time function. Therefore, the terms produce a variable plate current component and hence a changing stator field, resulting in motor motive power, and that such motive power continues as long as represents a change in the phase shift with frequency departure of the carrier from the resonant frequency of tuned circuit I2. It will be noted that the fields produced by the voltages EIEZ cos [45+(,f)l

are always 90 degrees out of phase, such quadrature relation being necessary for the motor described and claimed in the aforementioned United States Patent No. 1,959,449 to operate.

A comparison of the two quadrature variable fields, resulting from the two voltages E1Ez cos [45+(f)l which is the case of the same frequency but of variable phase shift with frequency, and which is involved in my invention, with the two quadrature variable fields, resulting from the two voltages which is the case of two dissimilar frequencies as.

described in United States Patent No. 1,959,449, it will be observed thatthe voltage expressions of these two variable fields are similar in form. (f) is a variable phase shift with frequency, and hence with time, since frequency varies with time; therefore, is also a (t).

The rotor 18' of the motor will rotate in one. direction forapositive phase shift and in the reverse direction for a negative phase shift, and such rotation will continue until tuned circuit 12 is resonant to the frequency of the incoming carrier. When this occurs the phase shift becomes zero, whereupon the motivating motor field ceases to vary, and hence the rotor will cease to turn until the frequency of the carrier again shifts.

While my invention has been described as applied to maintain a single sharply-tuned circuit in resonance with an incoming carrier wave, it could also be utilized to maintain a plurality of circuits having identical constants in resonance with an incoming carrier wave by utilizing thev rotation of the aforesaid tuning motor rotor to operate a small tuning capacitor, similar to capacitor 18, for each such circuit. Either the phase shift through one such circuit or the phase shift through a plurality of such identical circuits in cascade could be utilized to affect the resonance control. Fig. 3 shows my invention applied to a circuitof the latter type; Its operation is the same as'that of Fig. 1, except that the phase shift through two identical tuned circuits is utilized to effect the resonance control and an auxiliary tuning capacitor M3 for each tuned radio frequency stage is operated by the rotor [8 of the tuning motor. The rotors of capacitors l8 may be on the same shaft orbtherwise ganged.

The structure hereinabove described may be modified in proportion and arrangement of the parts by those skilled in the art without depart-' invention mental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A device for resonance control comprising a sharply-tuned circuit, means for applying an incoming carrier wave to said circuit, means for converting said carrier wave before application to said circuit to a first wave of lower frequency. means for converting said carrier wave after application to said circuit to a second wave of identical lower frequency, said circuit when out of resonance with said carrier wave producing a phase shift of said carrier wave, means for com pensating for all phase shift of said second wave with reference to said first wave not caused by said circuit being out of resonance with said in-- coming carrier wave, a split phase demodulating means, a self-starting synchronous motor having field windings and a rotor, said demodulator means having for its load impedance said field windings, means for applying both said first wave and said second wave to saiddemodulator means, said demodulator means being responsive to said phase shift caused by said circuit being out of resonance with said carrier wave to produce a varying field in said windings with consequent rotation of said rotor, a tuning means for said circuit actuated by said rotor, said rotor actuate ing said tuning means to resonate said circuit with said incoming carrier wave.

2. A device for resonance control comprising a tuned circuit, means for applying an incoming carrier wave to said circuit, means for converting said carrier wave before application to said circuit to a first wave of lower frequency, means for converting said carrier wave after application to said circuit to a second wave of identical lower frequency, said circuit when out 'of resonance with said carrier wave producing a phase shift of said carrier wave, means for compensating for all phase shift of said second wave with reference to said first wave not caused by said circuit being out of resonance with said incoming carrier wave, a demodulating means, a self-starting synchronous motor having field windings and a rotor, said demodulator means having for its load impedance said field windings, means for applying both said first wave and said second wave to said demodulator means, said demodulator means being responsive to said phase shift caused by said circuit being out of resonance with said carrier wave to produce rotation of .said rotor, a tuning means for said circuit actuated by said rotor, said rotor actuating said tuning means to resonate said circuit with said incoming carrier wave.

3. A device for resonance control comprising a tuned circuit, means for applying an incoming carrier wave to said circuit, means for converting said carrier wave before application to said circuit to a first wave of lower frequency, means for converting said carrier wave after application to said circuit to a second wave of identical lower frequency, said circuit when out of resonance with said carrier wave producing a phase shift of said carrier wave, a demodulating means, a self-starting synchronous motor having field windings and a rotor, said demodulator means having for its load impedance said field windings, means for applying both said first wave and said second wave to said demodulator means, said demodulator means being responsive to said phase shift to produce rotation of said rotor, a

tuning means for said circuit actuated by said rotor, said rotor actuating said tuning means to resonate said circuit with said incoming carrier wave.

4. A device for resonance control comprising a plurality of tuned circuits in cascade including a first circuit and a last circuit, means for applying an incoming carrier wave to said first circuit, means for converting said carrier wave before application to said circuit to a first wave of lower frequency, means for converting said carrier wave after application to at least one of said circuits to a second wave of identical lower frequency, said circuits when out of phase with said carrier wave producing a phase shift of said carrier wave, a demodulating means, a self-starting synchronous motor having field windings and a rotor, said demodulator means having for its load impedance said field windings, means for applying said first wave and said second wave to said demodulator means, said demodulator means being responsive to said phase shift to produce a varying field in said windings with consequent rotation of said rotor, a tuning means for said circuits actuated by said rotor, said rotor actuating said tuning means to resonate said circuits with said incoming carrier wave.

5. A device for resonance control, comprising a tuned circuit, means for applying an incoming carrier wave to said circuit, a tuning means for.

said circuit, said circuit when out of resonance with said wave causing a phase shift .ofsaid wave, a split-phase demodulator means, a self-starting synchronous motor having field windings and a rotor,,said modulator means having as its load impedance the field windings of said motor, means for applying said carrier wave to said demodulator means both before and after application to said circuit, said demodulator means being responsive to said phase shift to produce a rotating field in said field windings with consequent rotation of said rotor, said tuning means being actuated by said rotor to resonate said circuit with said incoming carrier wave.

6. A device for resonance control, comprising a tuned circuit, means for applying an incoming carrier wave to said circuit, a tuning means for said circuit, said circuit when out of resonance with said wave causing a phase shift of said wave, a demodulator means, a self-starting synchronous motor having field windings and a rotor, said demodulator means having as its load impedance the field windings of said motor, means for applying said' carrier wave to said demodulator means both before and after application to said circuit, said demodulator means being responsive to said phase shift to produce rotation of said rotor, said tuning means being actuated by said rotor to resonate said circuit with said incoming carrier wave.

7. A device for resonance control, comprising a tuned circuit, means for applying an incoming carrier wave to said circuit, a tuning means for said circuit, said circuit when out of resonance with said wave causing a phase shift of said wave, a split-phase demodulator means, a selfstarting synchronous motor having field windings and a rotor, said demodulator means having as its load impedance the field windings of said motor, means for applying said carrier wave to said demodulator means both before and after application to said circuit, means for compensating for all phase shift of said wave after application to said circuit with reference to said wave before application to said circuit not caused by said circuit being out of resonance with said incoming wave, said demodulator means being responsive to said phase shift caused by said circuit being out of resonance with saidincoming Wave to produce a rotating field in said field windings with consequent rotation of said rotor, said tuning means being actuated by said rotor to resonate said circuit with said incoming carrier wave.

8. A device for resonance control, comprising a tuned circuit, means for applying an incoming radio frequency carrier wave to said circuit, said carrier wave passing through said circuit, said circuit when out of resonance with said incoming carrier wave causing a phase shift of said carrier wave passing through said circuit, a tuning means for said circuit, a control means responsive to the phase difference between two radio frequency waves of the same frequency for actuating said tuning means, and means for applying said carrier wave both before and after passing through said circuit to said control means, said tuning means being actuated by said control means to resonate said circuit with said incoming carrier wave. Y

9. A device for resonance control, comprising a tuned circuit, means for applying an incoming radio frequency carrier wave of varying frequency to said circuit, said carrier wave passing through said circuit, said circuit when out of resonance with said incoming carrier wave causing a phase shift of said carrier wave passing through said circuit, a tuning means for said circuit, a control means responsive to the phase difference between two radio frequency waves of the same frequency for actuating said tuning means, and means for applying said carrier wave both before and after passing through said circuit to said control means, said tuning means being actuated by said control means to resonate said circuit with said incoming carrier wave, said control means requiring negligible radio frequency energy for its operation.

10. A device for resonance control comprising a plurality of tuned circuits in cascade including a first circuit and a last circuit, means for applying an incoming radio frequency carrier wave to said first circuit, a tuning means for said circuits, said carrier wave passing through said circuits, said circuits when out of resonance with said carrier wave causing a phase shift of said carrier wave passing through said circuits, a control means responsive to phase difference between two radio frequency waves of the same frequency for actuating said tuning means, means for applying said carrier wave both before and after passing through said circuits to said control means, said tuning means being actuated by said control means to resonate said circuits with said incoming carrier wave.

11. A device for resonance control comprising a plurality of tuned circuits in cascade including a first circuit and a last circuit, means for applying an incoming radio frequency carrier wave of varying frequency to said first circuit, a tuning means for said circuits, said carrier Wave passing through said circuits, said circuits when out of resonance with said carrier wave causing a phase shift of said carrier wave passing through said circuits, a control means responsive to phase difference between two radio frequency waves of the same frequency for actuating said tuning means, means for applying said carrier wave both before and after passing through said circuits to said control means, said tuning means being actuated by said control means to resonate said circuit with said incoming carrier wave, said control means requiring negligible radio frequency energy for its operation.

12. The method of maintaining the frequency of a tunable circuit substantially in resonance with an incoming radio frequency carrier wave of varying frequencies which includes the steps of producing a basic voltage with frequency determined by said wave, producing a second voltage with the same frequency as said basic voltage, said second voltage either lagging or leading said basic voltage, and differing from it in phase relation, as is determined by the divergence of the frequency of said carrier wave either above or below the resonant frequency of said tunable circuit, combining said basic voltage and said second voltage toproduce a first resultant voltage and a second resultant voltage, said first resultant voltage differing from said second resultant voltage in phase relation by 90, both said first resultant voltage and said second resultant voltage differing in phase relation from said carrier wave an amount in accordance with the variation of the frequency of said wave from the resonant frequency of said tunable circuit, producing a shifting flux field when said phase relation of said first resultant voltage and said second resultant voltage varies, and applying said shifting fiux field to produce mechanical motion for the purpose of tuning said tunable circuit with the use of negligible radio frequency energy.

13. The method of maintaining the frequency of a plurality of tunable circuits in cascade substantially in resonance with an incoming radio frequency carrier wave of varying frequencies which includes the steps of producing a basic voltage with frequency determined by said wave, producing a second voltage with the same frequency as said basic voltage, said second voltage either lagging or leading said basic voltage, and differing from it in phase relation, as is determined by the divergence of the frequency of said carrier wave either above or below the resonant frequency of said tunable circuits, combining said basic voltage and said second voltage to produce a first resultant voltage and a second resultant voltage, said first resultant voltage differing from said second resultant voltage in phase relation by both first resultant voltage and said second resultant voltage differing in phase relation from said carrier wave an amount in accordance with the variation of the frequency of said wave from the resonant frequency of said tunable circuits, producing a shifting flux field when said phase relation of said first resultant voltage and said second resultant voltage varies, and applying said shifting flux field to produce mechanical motion for the purpose of tuning said tunable circuits with the use of negligible radio frequency energy.

14. The method of maintaining the frequency of a tunable circuit substantially in resonance with an incoming radio frequency carrier wave of varying frequencies which includes the steps of producing a first electric current with frequency determined by said wave, producing a second electric current with the same frequency as said first current, said second current either lagging or leading said first current, and differing from it in phase relation, as is determined by the divergence of the frequency of said carrier wave either above or below the resonant fre quency of said tunable circuit, combining said first current and said second current to produce a third current and a fourth current, said third current differing from said fourth current in phase relation by 90, both said third current and said fourth current differing in phase relation from said carrier wave an amount in accordance with the variation of the frequency of said wave from the resonant frequency of said tunable circuit, producing a shifting flux field when said phase relation of said third current and said fourth current varies, and applying said shifting flux field to produce mechanical motion for the purpose of tuning said tunable circuit with the use of negligible radio frequency energy.

HERBERT G. LINDNER. 

